1. Field of the Invention
The present invention relates to a silver halide photographic emulsion and a photographic light-sensitive material containing this emulsion.
More specifically, the invention relates to a silver halide emulsion which has a low fog and is improved in a sensitivity and in a resistance to pressure particulary in the blue-sensitive layer, and also to a photographic light-sensitive material containing this emulsion.
2. Description of the Related Art
Recently, a demand for photographic silver halide emulsions has been increasingly strict, and higher-level demands have arisen for toughness, such as a resistance to pressure, in addition to photographic properties, such as a high sensitivity and a good graininess.
It is considered preferable in terms of uniformity of chemical sensitization that silver iodide (iodide ion) content be uniform within individual grain as well as among grains in order to increase the sensitivity of the grains.
JP-A-2-68538 (Japanese Patent Appln. No. 63-220187) discloses the technique of eliminating a nonuniform distribution of halide inside each grain and between individual grains by using, as a halogen ion supply source, either a halogen ion-releasing agent or silver halide fine grains in order to form grains in the process of forming silver halide grains, in place of an aqueous halogen salt solution which is conventionally used. ("JP-A" means Published Unexamined Japanese Patent Application.)
However, JP-A-2-68538 does not disclose that, to prepare an emulsion which has a low fog and is improved in a sensitivity and a resistance to pressure, it is important to form silver halide grains while iodide ions are rapidly being generated.
Hitherto it is known that the addition of a sensitizing dye increases the pressure marks, and research to improve the resistance to pressure has been made.
JP-A-63-220228 discloses tabular grains which have improved resistance to pressure.
The grains obtained by the technique disclosed in this publication, however, have a broad distribution of silver iodide content among themselves and are disadvantageous in terms of the uniformity of chemical sensitization.
The tabular grains have too low a resistance to pressure to be used in a blue-sensitive layer which is an upper layer of a silver halide photographic light-sensitive material, and a protective layer must be made thick.
Consequently, the advantageous property of the tabular grains, i.e., the property of improving the sharpness of lower layers, is not be utilized fully in practice.